Plastic articles and items with a pleasant haptic appearance, such as a textile-like touch, and good optics are desirable for numerous applications, including hygienic products or garments. To improve aesthetics, for example of a plastic film, various techniques of surface modification resulting in various surface structures have been employed. Known surface-structured films include apertured films and non-apertured films.
Surface-structured apertured films include films wherein the aperture is in the plane of the film, irrespective of any surface structure or pattern, and films which are apertured through the surface feature, e.g. the protruberance.
For example, U.S. Pat. No. 4,629,643 provides a micro-apertured polymeric web exhibiting a pattern of discrete volcano-like aberrations, the end of which includes at least one micro-aperture at its point of maximum amplitude. The films are produced by impinging a jet of high pressure liquid on the exposed surface of a web of flat polymeric film while said film is supported on a fine mesh woven wire support member. The high pressure fluid jet causes micro-aperturing of those portions of the web which coincide with the interstices between the intersecting woven wire filaments comprising the support member and which correspond to the surface aberrations after removal of the web.
U.S. Pat. No. 5,733,628 discloses a film laminate wherein the carrier material comprises a woven or non-woven fibrous material and an elastomeric three-dimensional apertured film.
Non-apertured surface structured films include films with solid or with hollow surface structures.
According to U.S. Pat. No. 5,814,413 surface-texturing of a polymer film is accomplished by taking advantage of the usually undesired phenomenon of melt fracture. The patent discloses extruded films which due to melt fracture show a rough surface texture.
International Patent Application WO 97/02128 provides a process for producing a surface-structured, sheet-like semi-finished product made from thermoplastic polymers. The resulting product is reported to have a velour-like or velvety surface with numerous solid fibrous projections which can be longer than 3 millimeters. According to the disclosed process, the thermoplastic material is extruded in the molten state onto a moving belt or roller surface which is covered with cavities or borings having a depth of between 2 and 4 millimeters. The roller surface is exposed to a vacuum from the outside thus removing the air from the cavities and enabling these to be filled with the thermoplastic material. After solidification of the thermoplastic material, the semi-finished product covered with fiber-like projections is peeled off the surface.
International Patent Application WO 99/47339 describes a method for producing a surface-structured, film-like semi-finished product from a thermoplastic comprising forming a pile consisting of solid protuberances and elongating the protruberances by combing, brushing, knife-coating and/or shear pinching.
International Patent Application WO 99/16608 discloses a method for making an embossed oriented film. Said method discloses the steps of softening at least one of the two major surfaces of an oriented film, embossing the softened surface(s), and cooling the resulting embossed oriented thermoplastic film. In order to maintain orientation the combined steps of softening, embossing and cooling should occur within a second.
International Patent Application WO 99/06623 provides a unitary polymer substrate having a plurality of solid microfibers which may have a variety of forms, such as frayed-end microfibers, tapered microfibers, microfibers having an expanded cross-sectional shape and microfibers having a high aspect ratio. The microfibers are reported to increase the surface area and to impart a cloth-like feel.
International Patent Application WO 00/16965 relates to a method for producing a surface-structured, film-like semifinished product made of a thermoplastic which is applied onto a surface covered with fine cavities. The solidified plastic is removed from the surface as a structured film. The disclosed structure is a pile comprised of solid projections and naps which may be stretched, e.g. by brushing.
Films with bubble-like surface features which are hollow from the bottom are disclosed, for example, in U.S. Pat. No. 4,463,045, International Patent Application WO 96/13979 and U.S. Pat. No. 5,192,484.
U.S. Pat. No. 5,792,411 suggests replicated articles with surface structures which have a suction cup geometric configuration.
There still is the need for plastic articles showing improved properties, particularly excellent aesthetics, as reflected in a textile-like haptic appearance and low gloss. Further representative properties desirable for plastic articles include, for example, increased surface area, variability of the surface appearance, anti-slip behavior, controlled storage, release or carrier properties, controlled thermal and barrier performance, as well as any combination thereof.
It is an object of the present invention to meet these needs. It is an object of the present invention to provide surface-structured plastic films, sheets or coatings with hollow surface structures which can be specifically designed to meet the desired performance attribute(s) and can be produced in a cost effective way. In particular, it is one object of the present invention to provide a plastic article having a soft, velvety and cloth-like touch in combination with a mat appearance. It is another object to provide a plastic article having an increased surface area. It is yet a further object of the present invention to provide a plastic article with an imprintable surface. The present invention also addresses the problem of providing a plastic article having a frictional behavior indicating anti-slip properties. It is a particular object of the present invention to provide a plastic article, which displays any desired combination of the above-mentioned properties, and may afford additional advantageous performance attributes depending on the intended end-use application(s).
The objects of the present invention are achieved by providing a film, sheet, or coating, which is characterized by a distinct morphology. Such morphology is reflected in the presence of at least one layer having a fringed surface microstructure and, optionally, of further layers affording certain additional functions, for example, heat sealability, bulk or mechanical properties. The morphology and composition of the film, sheet or coating of the invention can be tailored to satisfy the particular requirements of the production process and the intended end-use application(s).